MSRP Map

Mangroves

Mangrove ecosystems are a mosaic of different types of forest, with each type providing different physical habitats, topology, niches, microclimates, and food sources for a diverse assemblage of animals. Mangroves have important structural properties including: the trapping and stabilization of intertidal sediments; the formation of organic soils and mucks; providing protection from wave and wind erosion; providing a dendritic vegetative reef surface in the subtidal and intertidal zones; and forming a structural complex of a multibranched forest with a wide variety of surface habitats (Savage 1972).

Red Mangrove

Red mangroves are distinguished by the dendritic network of aerial prop roots extending from the trunk and lower branches to the soil. The prop roots are important adaptations to living in anaerobic substrates and providing gas exchange, anchoring system, and absorbing ability. Within the soils, microroots stabilize fine silts and sands maintaining water clarity and quality. Red mangroves may attain heights of 25 to 38 m (82 to 125 ft) in the rich deltas of riverine forests, but average 8 to 10 m (26 to 33 ft) on most fringing shorelines, and occur as smaller trees at their northern extents or in marginal habitats such as the coral rock salt ponds of the Florida Keys. Bark is grey and the interior red. Red mangroves can form a variety of crown shapes from short continuous scrubby crown to uneven discontinuous crowns. As trees age, gaining size and putting down large prop root supports, significant horizontal as well as vertical growth occurs. This horizontal growth habit has led to the metaphor of walking trees. The leaves are shiny, deep green on the surface and paler underside. Flowers are small, white, four-petalled, four-bracted, and wind pollinated. The germinated seed produces a long (25 to 30 cm, or 10 to 12 in) pencil or torpedo-shaped propagule.

Black Mangrove

Black mangroves have distinctive horizontal cable roots that radiate from the tree with short, vertically erect aerating branches (pneumatophores) extending 2 to 20 cm (0.8 to 7.9 in) above the substrate. The trees grow straight, attaining heights of 40 m (131 ft) and averaging 20 m (66 ft). The bark is dark and scaly. They have narrow, elliptic or oblong leaves that are shiny dark green above and pale almost cream green with short dense hairs below. The upper surface of leaves can be encrusted with salt excreted by the tree. The bilaterally symmetric white flowers are showy and pollinated by Hymenoptera (Tomlinson 1986). The black mangrove is the source of mangrove honey. The germinated seed produces a lima bean size and shaped propagule (Odum and McIvor 1990). Black mangroves are shade tolerant and sun intolerant when immature (Snedaker 1982). As it matures, the black mangrove becomes shade intolerant. This provides different growth forms in immature and mature trees.

White Mangrove

White mangroves grow either in tree form or shrub form up to heights of 15 m (49 ft) or more. The growth form tends to be erect. Some white mangroves form erect, blunt-tipped pneumatophores if growing in anaerobic or chemically stressed soils. Bark is white and relatively smooth. Leaves are fleshy, flattened ovals with rounded ends. The same pale green color is on both upper and lower surfaces. Two glands are found at the apex of the petiole that excrete salt and extra floral nectar. Small yellowish flowers are found in alternate rows on the terminal ends of branches. These germinate into small football-shaped propagules (1 to 1.5 cm, or 0.4 to 0.6 in). In the northern part of their range, white mangroves may not propagate on the tree and true propagules are not formed.

All three mangrove species flower in the spring and early summer. Propagules fall from late summer through early autumn.

Buttonwood

Buttonwoods grow to 12 to14 m (39 to 46 ft) in height in a shrub or tree form, but do not produce a true propagule in Florida (Tomlinson 1986). Bark is grey and very furrowed providing attachment for epiphytes. Leaves are thin, broad to narrow, and pointed. There are two morphotypes: the green with medium green leaves found on peninsular Florida and the silver with pale pastel green leaves historically limited to the Florida Keys but now widespread by nursery practices. It is thought the silver buttonwood is an adaptation to the rocky, dry habitats associated with the Keys archipelago. Two glands are found at the apex of the petiole that excrete extra floral nectar and salt. Tiny brownish flowers are found in a sphere on the terminal ends of branches. These produce a seed cluster known as the button. Buttonwoods are able to grow in areas seldom inundated by tidal waters. The mangrove adaptations to the osmotic desert of salt water, also adapted buttonwoods to arid areas of barrier islands and coastal strands.

Taken from: U.S. Fish and Wildlife Service. 1999. South Florida Multi-Species Recovery Plan.   Atlanta, Georgia. Pp.3:522-524.

Listed Species Occurring in Mangrove Habitat

  • Florida Panther
  • Key Deer
  • Lower Keys Rabbit
  • West Indian Manatee
  • Everglades Snail Kite
  • Wood Stork
  • American Crocodile
  • Bald Eagle
  • Rice Rat
  • Eastern Indigo Snake